1. Field of the Invention
The present invention relates to an AC type plasma display used for a flat type television and information representing display; and a driving apparatus of the display and a driving method of the display. More particularly, the present invention relates to an AC type plasma display for restricting incorrect discharge and a driving apparatus of the display and a driving method of the display.
2. Description of the Related Art
In general, a plasma display panel (hereinafter, abbreviated as PDP) has a number of features including thin structure, flickering-free, large display contrast ratio, possible comparatively large screen, high response speed, spontaneous light emitting type, possible multiple color light emission by use of a phosphor. Thus, recently, in the field of computer associated display device and in the field of color image display or the like, a PDP becomes more popular. This PDP is divided into two types: an AC type in which an electrode is covered with an dielectric to indirectly cause operation in an AC discharge and a DC type in which an electrode is exposed in a discharge space to cause operation in a DC discharge state, depending on its operating system. Further, this AC type PDP is divided into a memory operation type using a discharge cell memory as a driving system and a refresh operation type that does not use such memory as a driving system. The luminescence of the PDP is proportional to discharge count, that is, the number of pulse voltage repetitions. About the above refresh type, when a display capacity increases, the luminescence is lowered. Thus, such a PDP is mainly used as a PDP with its small display capacity.
FIG. 1 is a schematic perspective view illustrating a configuration of one display cell of a conventional AC memory operation type PDP.
Two insulation substrates 1 and 2 made of glass are provided at the conventional AC memory operation type PDP. The insulation substrate 1 serves as a rear substrate, and the insulation substrate 2 serves as a front substrate.
Transparent scan electrodes 3 and transparent sustainment electrodes 4 are provided at an opposite side to the insulation substrate 1 in the insulation substrate 2. The scan electrode 3 and the sustainment electrode 4 extend in horizontal direction (transverse direction) of the panel. In addition, trace electrodes 5 and 6 are disposed so as to be overlapped respectively on the scan electrode 3 and the sustainment electrode 4. The trace electrodes 5 and 6 are metallic, for example, and are provided in order to reduce an electrode resistance value between each of these electrodes and an external driving apparatus. Further, there are provided an dielectric layer 12 covering the scan electrode 3 and the sustainment electrode 4 and a protective layer 13 comprising a magnesium oxide or the like, for protecting the dielectric layer 12 from discharge.
Data electrodes 7 orthogonal to the scan electrodes 3 and the sustainment electrodes 4 are provided at an opposite face to the insulation electrode 2 in the insulation electrode 1. Therefore, the data electrode 7 extends in vertical direction (longitudinal direction) of the panel. In addition, bulkheads 9 for partitioning display cells in horizontal direction are provided. Further, a dielectric layer 14 covering the data electrode 7 is provided, and phosphor layers 11 for converting the ultraviolet rays generated by discharge of a discharge gas into a visible light 10 are formed on each of the side face of the bulkheads 9 and on the surface of the dielectric layer 14. Discharge gas spaces 8 are allocated by the bulkheads 9 in a space between the insulation substrates 1 and 2. In this discharge gas space 8, a discharge gas comprising helium, neon, xenon or the like, or a mixture containing these is charged.
FIG. 2 is a block diagram depicting driving circuits in a conventional AC memory operation type DPD. In addition, FIG. 3A is a circuit diagram depicting driving circuits on the scan electrode 3 side; FIG. 3B is a circuit diagram depicting driving circuits on the sustainment electrode 4 side; and FIG. 3C is a circuit diagram depicting a data driver 28.
There are provided display cells that emit light at a cross point between the scan electrode 3 and sustainment electrode 4 provided in parallel to each other and the data electrodes 7 orthogonal to the electrodes 3 and 4. Therefore, one scan electrode, one sustainment electrode, and one data electrode are provided in one display cell. Thus, the number of display cells on the entire screen is xe2x80x9cn+mxe2x80x9d, where the number of scanning and sustainment electrodes is xe2x80x9cnxe2x80x9d, and the number of data electrodes is xe2x80x9cmxe2x80x9d.
In addition, a removal portion of a respective one of the scan electrodes 3 and sustainment electrodes 4 is provided at the end in the horizontal direction of the display panel in a conventional PDP, and a driving circuit is connected to this removal portion.
A scan pulse driver 21 for outputting scan pulses to each of the scan electrodes 3 is provided as a driving circuit at the scan electrode 3 side. In addition, a reset driver 30 for outputting reset pulses common to all of the scan electrodes 3; a sustainment driver 23 for outputting sustainment pulses; an erasing driver 24 for applying erasing pulses; a scan base driver 25 for outputting scan base pulses; and a scan voltage driver 26 for outputting a scan voltage are connected to a scan pulse driver 21.
On the other hand, a sustainment driver 27 for applying sustainment pulses to the entirety of the sustainment electrode 4 is provided as a driving circuit at the sustainment electrode 4 side.
Further, a removal portion of the data electrodes 7 is provided at the end in the vertical direction of the display panel in a conventional PDP, and to this removal portion, a data driver 28 is connected as a driving circuit.
A controller 29 for switching operation of each driver according to a video signal is provided.
An operation of a conventional PDP configured as described above will be described hereinafter. FIG. 4 is a timing chart showing a method of driving the conventional PDP.
In FIG. 4, periods 1-f and 1-(f+1) are reset periods of a sub-field of a respective one of the frames xe2x80x9cfxe2x80x9d and xe2x80x9cf+1 xe2x80x9d. In these reset periods, respective rectangular wave reset pulses Ppr-s and Ppr-c are applied to the entirety of the scan electrodes S and the entirety of the sustainment electrodes C.
In the reset periods 1-f and 1-(f+1), reset discharge is generated in a discharge space in the vicinity of a gap between the scan electrode and the sustainment electrode of all display cells, depending on a positive polarity rectangular wave applied to the scan electrode and a negative polarity rectangular wave applied to the sustainment electrode. In this manner, the generation of active particles which makes it easy to generate discharge of display cells is performed. At the same time, the negative polarity wall charge is accumulated on the scan electrode S, and the positive electrode wall charge is accumulated on the sustainment C. However, these wall charges are almost eliminated by self-erasing discharge in a subsequent fall of the pulse.
Then, the erasing pulse Pe-s is applied to the entire of the scan electrodes S, whereby the wall charges which are not erased by self-discharge are completely erased.
In FIG. 4, periods 2-f and 2-(f+1) are addressing periods of a sub-field of a respective one of the frames xe2x80x9cfxe2x80x9d and xe2x80x9cf+1xe2x80x9d. In these addressing periods 2-f and 2-(f+1), the entirety of the sustainment electrodes C is maintained to a GND level. In addition, a negative polarity scan pulse Psc-s is applied to a scan electrode Si in a row in which writing is to be performed, and a positive polarity data pulse Pd is applied to a data electrode D. As a result, both of these pulses are applied, and an opposite discharge is generated in a selected display cell. With this discharge being a trigger, a planer discharge is generated as a writing discharge between a sustainment electrode Ci and a scan electrode Si. Thus, a negative charge is accumulated on the scan electrode Si, and a positive charge is accumulated on the sustainment electrode Ci.
On the other hand, a gap between electrodes is large between the sustainment electrode Ci-1, which is positioned on the upper side of the scan electrode Si, and the scan electrode Si in other display cells, and thus, a planar discharge is not generated. In this way, writing discharge is generated at only a cross point between the scan electrode Si to which the scan pulse Psc-s is applied and the data electrode D to which a data pulse Pd is applied.
In FIG. 4, periods 3-f and 3-(f+1) are sustainment periods of a sub-field of a respective one of the frames xe2x80x9cfxe2x80x9d and (f+1). In these sustainment periods 3-f and 3-(f+1), a sustainment pulse Psus-c is applied to the sustainment electrodes C, and then, the respective negative polarity sustainment pulses Psus-s and Psus-c are applied alternately to the scan electrodes S and the sustainment electrodes C.
In a display cell selectively written in the addressing period 2-f or 2-(f+1), the negative charge is accumulated on the scan electrodes S, and the positive charge is charge on the sustainment electrodes C. Thus, by applying the first sustainment pulse Psus-c, the negative polarity sustainment pulse voltage for the sustainment electrodes C and the wall charge voltage are weighted each other, a potential difference between electrodes exceeds a minimum discharge voltage, and a discharge is generated. Once the discharge is generated, a wall charge is disposed so as to cancel the voltage applied to each electrode. Therefore, a negative charge is accumulated on the sustainment electrodes C, and a positive charge is accumulated on the scan electrodes S.
In the next sustainment pulse, a negative voltage pulse is applied to the side of the scan electrodes S, and weighting relevant to a wall charge is generated in the scan electrodes S, a potential difference between the electrodes exceeds a minimum discharge voltage, and a discharge is generated. Then, in the sustainment periods 3-f and 3-(f+1), the sustainment pulses Psus-c and Psus-s are repeatedly applied, whereby the light emission of a selected display cells is sustained.
One sub-field of the frame xe2x80x9cfxe2x80x9d is configured in accordance with the steps from the periods 1-f to 3-f, and this sub-field is repeatedly formed in required times to configure the frame xe2x80x9cfxe2x80x9d. In addition, one sub-field of the frame xe2x80x9cf+1xe2x80x9d is configured in accordance with the steps from the periods 1-(f+1) to 3-(f+1), and this sub-field is repeatedly formed in required times to configure a frame xe2x80x9cf+1xe2x80x9d.
In this conventional PDP driving method, a scan electrode and a sustainment electrode are always used in pair. Thus, in the case where writing is performed for a display cell in the n-th line, in order to restrain diffusion of discharge to display cells in the adjacent the (nxe2x88x921)-th line and the (n+1)-th line, it is required to set a gap between electrodes on which a discharge is not performed generally (such as between the n-th line scan electrode and the (nxe2x88x921)-th line sustainment electrode) to be larger than compared with that between electrodes on which a discharge is performed. For example, when a gap between discharge electrodes is set to 50 to 100 micrometers, it is required to set a gap between non-discharge electrodes to 250 to 400 micrometers. In this case, even if an attempt is made to reduce a pixel pitch in order to increase display resolution, a gap between non-charge electrodes cannot be reduced. Thus, there has been a problem that an area for electrodes itself may be reduced, and the light emission luminescence is lowered. In addition, the number of scan drivers must be the same as that of scanning lines. Thus, when the resolution in vertical direction is increased, a required number of drivers increases, which increases circuit cost. Hereinafter, such a PDP is referred to as a first prior art.
Because of this, there is proposed a plasma display for switching a portion targeted for performing sustainment and light emission every frame and a driving method thereof (Japanese Patent No. 2801893). Hereinafter, this conventional plasma display is referred to as a second prior art. FIG. 5 is a schematic view illustrating a light emission portion in the scanning period of a frame xe2x80x9cfxe2x80x9d in the second prior art; FIG. 6 is a schematic view illustrating a light emission portion in the sustainment period of a frame xe2x80x9cfxe2x80x9d in the second prior art; FIG. 7 is a schematic view illustrating a light emission portion in the scanning period of a frame xe2x80x9cf+1xe2x80x9d in the second prior art; and FIG. 8 is a schematic view illustrating a light emission portion in the sustainment period of a frame xe2x80x9cf+1xe2x80x9d in the second prior art.
In the second prior art, at the frame xe2x80x9cfxe2x80x9d, as shown in FIG. 5, writing is performed for an addressing period by planar discharge between the scan electrode Si-1 and the sustainment electrode Ci-1 with an opposite discharge generated between the scan electrode Si-1 and the data electrode D being a trigger, for example. As shown in FIG. 6, in the subsequent sustainment periods, sustainment voltages are applied alternately between the scan electrode Si-1 and the sustainment electrode Ci-1, and sustainment and light emission are performed, thereby causing display.
In addition, at the frame xe2x80x9cf+1xe2x80x9d, as shown in FIG. 7, writing is performed for an addressing period by a planer discharge between the scan electrode Si and the sustainment electrode Ci-1 with an opposite discharge generated between the scan electrode Si and the data electrode D being a trigger, for example. As shown in FIG. 8, sustainment voltage is applied alternately between the scan electrode Si and the sustainment electrode Ci-1 in the subsequent sustainment period, and sustainment and light emission are performed, thereby causing display.
In the second prior art, all the gaps between electrodes may become discharge gaps. Thus, in order to generate a stable planar discharge in a gap between electrodes to be performed discharge (for example, a gap between the scan electrode Si-1 and the sustainment electrode Ci-1 in the frame xe2x80x9cfxe2x80x9d), the sustainment electrodes C are divided into an odd number sustainment electrode group Codd and an even number sustainment electrode group Ceven. In displaying the frame xe2x80x9cfxe2x80x9d, as shown in FIG. 5, a positive pulse is applied to the odd number sustainment electrode group Codd, whereby a potential difference from the scan electrode S is increased. On the other hand, a negative pulse is applied to the even number sustainment electrode group Ceven, whereby a potential difference from the scan electrode S is reduced. In addition, in displaying the frame xe2x80x9cf+1xe2x80x9d, as shown in FIG. 7, a pulse having its polarity reverse from the frame f is applied to each of the sustainment electrode groups. In the second prior art, a gap between electrodes in which planer discharge is thus performed is selected.
In addition in a sustainment period as well, as shown in FIG. 6 and FIG. 8, a phase of a sustainment pulse to be applied is changed so that a potential in gap between electrodes on which a sustainment discharge is not performed is the same as another potential.
According such second prior art, all the gaps between electrodes become discharge gaps, that is, all the gaps between electrodes are equal to each other. Thus, a decrease in an electrode area in the case where resolution is increased becomes smaller, and a decrease in a light emission luminescence becomes smaller. In addition, because of interlace driving method, in which light emission portions are changed for each frame, the display capacity in vertical direction can be increased without increasing the number of drivers.
However, according to the second prior art, all the gaps between electrodes become gaps between discharge electrodes. In a sustainment period, an electrode on which no discharge is to be generated has the same sustainment wave forms. Therefore, as shown in FIG. 5 and FIG. 6, for example, in the case where, in displaying the frame xe2x80x9cfxe2x80x9d, a discharge is performed between the scan electrode Si-1 and the sustainment electrode Ci-1 and a discharge is not performed between the scan electrode Si and the sustainment electrode Ci, if sustainment discharge is repeated, the charge on the sustainment electrode Ci-1 gradually diffuses on the side of the scan electrode Si, and an incorrect discharge may be generated between the scan electrode Si and the sustainment electrode Ci. In addition, as shown in FIG. 8, in displaying the frame xe2x80x9cf+1xe2x80x9d as well, a similar incorrect discharge may occur.
Such an incorrect discharge is likely to occur when a sustainment voltage increases. Thus, there is a problem that the sustainment voltage setting range must be narrowed. In addition, it is required to apply two types of sustainment pulses with their different phases each other to the scan electrode and the sustainment electrode, thus causing an increased circuit cost.
It is an object of the present invention to provide an AC type plasma display capable of improving resolution in vertical direction, and capable of expanding an operating voltage range with a low background illumination and a good dark site contrast; a driving apparatus of the display and a driving method of the display.
An AC type plasma display according to one aspect of the present invention comprises: first and second substrate disposed oppositely; scan electrodes and sustainment electrodes provided alternately at an opposite face side to the second substrate in the first substrate, the scanning and sustainment electrodes extending in a row direction; data electrodes provided at an opposite face side to first substrate in the second substrate, the date electrodes extending in a column direction; and auxiliary electrodes provided at all of spaces between the scan electrodes and the sustainment electrodes, the auxiliary electrodes extending in a row direction.
In the present invention, auxiliary electrodes that extend in row direction are provided between all the scan electrodes and the sustainment electrodes. Thus, a signal to be applied to an auxiliary electrode is properly changed, whereby incorrect discharge can be prevented from occurring on interlace display.
If a signal to be applied to auxiliary electrodes (bias potential and driving signal) is switched between an odd number and an even number during addressing period between first and second frames, a portion at which an addressing discharge is generated is switched by each frame, and interlace display is performed. Thus, a gap between electrodes, i.e., between all the scan electrodes and the sustainment electrodes contributes to light emission, and high resolution display can be performed. In addition, if a bias potential is applied to an auxiliary electrode at which addressing is not performed, incorrect discharge is prevented, making it possible to expand a margin of an operating voltage.
In addition, if a signal supplied to an auxiliary electrode during addressing period is switched between a bias potential and a driving signal applied to a sustainment electrode, there is no need to apply a scan pulse to an auxiliary electrode, and a driving device is simplified, thereby making it possible to ensure cost reduction. In addition, a bias potential can be controlled independently, thus facilitating its optimization, and an operating voltage margin is expanded more significantly.
Further, if a potential of one auxiliary electrode is held to a bias potential in a sustainment period, reducing a potential difference between an auxiliary electrode and each of the scanning and sustainment electrodes adjacent to the auxiliary electrode. Thus, incorrect discharge between these electrodes is more unlikely to occur.
According to another aspect of the present invention, a driving device which drives the AC type plasma display comprises: a driving portion connected to the sustainment electrodes, scan electrodes, and auxiliary electrodes; and a controller. The controller controls operation of the driving portion to, in each sub-field that configures a first frame, hold a potential of auxiliary electrodes disposed at descending odd numbers at an arbitrary bias potential between a sustainment voltage applied to the sustainment electrodes during a sustainment discharge and a grounding potential at least during an addressing period, and apply a signal identical to a driving signal to be applied to one electrode selected from the group comprising the sustainment electrodes and scan electrodes to the auxiliary electrode disposed at the descending even numbers, and in each sub-field that configures a second frame, hold a potential of the auxiliary electrode disposed at even numbers at the arbitrary bias potential at least during the addressing period, and apply the signal identical to a driving signal to be applied to the one electrode to the auxiliary electrode disposed at odd numbers.
According to another aspect of the present invention, a driving method of the AC type plasma display comprises the steps of: holding a potential of auxiliary electrodes disposed at descending odd numbers at an arbitrary bias potential between a sustainment voltage applied to the sustainment electrodes during a sustainment discharge and a grounding potential at least during an addressing period, and applying a signal identical to a driving signal to be applied to one electrode selected from the group comprising the sustainment electrodes and scan electrodes to the auxiliary electrode disposed at the descending even numbers, in each sub-field that configures a first frame; and holding a potential of the auxiliary electrode disposed at even numbers at the arbitrary bias potential at least during the addressing period, and applying the signal identical to a driving signal to be applied to the one electrode to the auxiliary electrode disposed at odd numbers, in each sub-field that configures a second frame.